1. Indeed, the mutations that the family has undergone in this century have been more challenging than at any time of its evolution.


2. Thus, we have nuclear families, single parent families, surrogate families and global families to name just a few.


3. How these changes have reduced our world view is an interesting field of study in themselves.


4. What we often forget is that the family as it exists today has expanded its orthodox definition to include several variations.


5. Each of these has brought it own attitudes and priorities.

Which sentence should come fourth in the paragraph ?